According to a serial communication in conformity to Serial Attached SCSI (SAS) 2.0, a negotiation using an out-of-band (OOB) signal is conducted before a data transfer is initiated. The OOB signal has a pattern composed of (i) a DATA interval during which the OOB signal alternates between a high level (voltage) and a low level (voltage) and (ii) an IDLE interval during which the OOB signal is kept at an intermediate level (voltage) that is between the high level and the low level. According to a serial communication in conformity to PCI Express (PCIe) 3.0, a negotiation using a signal similar to the OOB signal is conducted. Note that, in a case of the serial communication in conformity to PCIe 3.0, an IDLE interval, included in a signal which is transmitted or received while the negotiation is conducted, is alternatively referred to as an Electrical Idle (EI) interval.
Such a serial communication has been conventionally made with use of a metal cable 101 illustrated in FIG. 15. The metal cable 101 includes a cable 104 and connectors 102 and 103 which are provided at respective ends of the cable 104. The cable 104 houses a metal wire 107 which serves as a transmission medium. The connectors 102 and 103 include AC coupling capacitors 105 and 106, respectively. With use of such a metal cable 101, it is possible for the connector 103 to output a voltage signal having a waveform identical to that of a data signal supplied to the connector 102, even in a case where the data signal is an OOB signal or the like (including a signal such as a signal having a pattern which is composed of (i) a DATA interval used in PCIe 3.0 and (ii) an EI interval, which signal is similar to an OOB signal used in SAS 2.0. The same explanation applies to the following descriptions.)